1. Field of the Invention
The invention relates to a vehicle body structure of, for example, an automobile, and more specifically to a vehicle lower body structure that includes a cross member which extends in the vehicle-width direction.
2. Description of the Related Art
There is a vehicle lower body structure of an automobile in which a step portion, a so-called raised portion (kick-up portion), is formed on a floor of a vehicle compartment. Japanese Patent Application Publication No. 2006-290140 (JP-A-2006-290140) (refer especially to abstract and FIG. 3) describes a vehicle lower body structure of this type. According to JP-A-2006-290140, a second raised portion (5) is formed in a floor panel (2) at a middle portion in the front-rear direction, and the second raised portion (5) is provided with cross members (14A, 16) that extend in the vehicle-width direction and that form closed section portions (15A, 17).
In the vehicle lower body structure described in JP-A-2006-290140, the second raised portion (5) is provided with the cross members (14A, 16) that form the closed section portions (15A, 17), and the cross members (14A, 16) are arranged separately. The cross member (16) is provided at an upper portion of the second raised portion (5), and the cross member (14A) is provided at a lower portion of the second raised portion (5). Therefore, in order to increase the buckling strength of the second raised portion (5) in the lateral direction of a vehicle body and the bending strength of the second raised portion (5) in the front-rear direction of the vehicle body, the cross members (14A, 16) need to be upsized or the thickness of the cross members (14A, 16) need to be increased. However, upsizing of the cross members (14A, 16) or an increase in the thickness of the cross members (14A, 16) results in an increase in the weight of the vehicle body.